What format can I enter repeat intervals in?

Repeat 'Every...'

For example, Bob wants to be reminded to pay the rent (on his waterfront apartment,
which costs far too much, but the view is great!). So, he adds a task and sets it to repeat 'Every Week'.

Examples of ways you can repeat 'Every' are:

Repeat

Every Tuesday

Every Monday and Wednesday

Every weekday

Every day

Every week

Every 2 weeks

Every month

Every 6 months

Every year

Every month on the 4th

Every month on the 3rd Tuesday

Every month on the last Monday

Every month on the 2nd last Friday

Every week until 1/1/2007

Every week for 20 times

Repeat 'After...'

These tasks only repeat after you've completed them. For example, you might enter a task to 'Clean the fridge'.
After you've completed that task, you might want to be reminded 'After 3 months' that it's time to clean the fridge again.

Examples of ways you can repeat 'After' are:

Repeat

After 5 days

After a week

After 6 months

After a year

A note about task properties

Task properties behave a bit differently between tasks set to repeat 'Every...' and those set to repeat 'After...'.

Tasks that repeat 'Every' create a task series: task properties and notes are common across all instances of the task.

Tasks that repeat 'After' work a bit differently: these do not create a task series, but rather create a new, independent task each time a task is generated. Task properties are copied from the previous instance. Each 'after' task has its own properties and notes, and isn't tied to other tasks. Additionally, notes are not copied from previous instances.